Mangrove (Avicennia marina subsp. australasica) litter production and decomposition in a temperate estuary

Mangrove forests can provide important cross-boundary subsidies of organic matter to adjacent habitats through the production, export, decomposition and assimilation of litter. We quantified two of these components in a temperate mangrove forest in Whangamata Harbour, New Zealand: 1) litter production; and 2) decomposition rates as a function of tidal elevation, sediment type and burial depth. Litter traps sampled monthly for a year measured an annual detrital input of 3.24–5.38 t DW ha^?1, of which 77% occurred in summer. Decomposition rates depended on litter type, with leaves decomposing faster (63 d to decay by 50%) than pneumatophore and wood material (316 and 460 d, respectively). Buried leaf and wood litter decomposed 1.3–1.4 times slower than litter on the sediment surface; however, tidal elevation and sediment type (mud vs. sand) had no effect. The slow decay of litter (an order of magnitude slower than tropical mangrove litter) suggests that its incorporation into temperate marine food webs may be relatively slow.     

Stable Carbon and Nitrogen Isotopic Characterization of Organic Matter in a Mangrove Ecosystem on the Southwestern Coast of Thailand

Organic matter in a tropical mangrove ecosystem was characterized by stable carbon and nitrogen isotopic analyze, conducted on various organic samples, including land and mangrove plants, soils, particulate organic matter (POM), and sea and river sediments along the southwestern coast of Thailand. The δ¹³C values of land plants and POM in river water can be explained in terms of a greater influence of C₃ plants than C₄ plants in this area. The POM and sediments from the Trang River and Ko Talibong area showed systematically higher δ¹⁵N values than those from Ko Muk and other coastal areas. Organic matter in the Trang River might be influenced by nitrogen released from agricultural or human waste, which could affect the isotopic composition of POM and sediments in the Trang River estuary and along the coast near the river mouth. We used a stochastic method to estimate the contributions of four organic end-members, identifiable by their δ¹³C and δ¹⁵N values. The results implied that seagrasses were a major source of sedimentary organic matter, contributing 42 ± 5% in the Ko Muk area and 36 ± 5% in the Ko Talibong area. The contribution of coastal POM to sediments was estimated to be only 13% in Ko Muk and 19% in Ko Talibong. Mangrove plants contributed approximately 23% in both areas. It was concluded that seagrasses are an important source of sedimentary organic matter in this coastal region of southwestern Thailand. This revised version was published online in August 2006 with corrections to the Cover Date.     

Seasonal Variations in Benthic Community Metabolism and Nitrogen Dynamics in a Shallow, Organic-Poor Danish Lagoon

The dynamics of benthic primary production and community respiration in a shallow oligotrophic, marine lagoon (Fællestrand, Denmark) was followed for 1·5 years. The shape of the annual primary production cycle was explained primarily by seasonal changes in temperature (r² = 0·67-0·72) and daylength (r² = 0·63), whereas temperature almost explained all variation in benthic community respiration (r² = 0·83-0·87). On a daily basis the benthic system was autotrophic during spring and summer supplied by 'new' and 'regenerated' nitrogen and predominantly heterotrophic during fall and winter caused by light and nutrient limitation. The linear depth-relationship between porewater alkalinity and ammonium indicated that the C:N ratio of mineralized organic matter is low in spring and summer (3-6) and high in fall and winter (9-16). This is inversely related to net primary production and thus the input of labile, nitrogen-rich algal cells. Accordingly, mineralization occurred predominantly in the upper 2-5 cm of the sediment. The pool of reactive material (microalgal cells) was estimated to account for 12% of total organic carbon in the upper 3 cm, and had an average turnover time of less than 1 month in summer. Assimilation of organic carbon by benthic animals was equivalent to about 30% of the annual gross primary production. Grazing reduced chlorophyll a concentration in the sediment during summer and spring to values 30-40% lower than in winter, but maintained a 3-4 times higher specific microalgal productivity. The rapid turnover of organic carbon and nitrogen, and important role of benthic microalgae showed that the benthic community in this oligotrophic lagoon is of a very dynamic nature.     

Diurnal variation of nitric oxide emission flux from a mangrove wetland in Zhangjiang River Estuary,China

The diurnal variation of nitric oxide (NO) emission fluxes from a Kandelia obovata and Avicennia marina mangrove wetland were studied in the Zhangjiang River Estuary Mangrove National Nature Reserve using a dynamic chamber-based technique and a chemiluminescent analyzer. Results from field experiments show that NO emission from K. obovata and A. marina sampling sites reached maximal values of 1.07 ng N m⁻² s⁻¹ and 1.23 ng N m⁻² s⁻¹, respectively after the night tide. Meanwhile NO emission maintained at a steady lower level in daytime for both wetland sites. In laboratory experiments, NO emission from the mangrove wetland soil samples treated with simulated tides in the darkness exhibited higher values than those in the light, therefore it seems that tides and darkness could increase NO emission from mangrove wetlands, while intensive light, high temperature, and dryness in the daytime decreased NO emission. Compared with K. obovata soil samples, the diurnal average NO emission rate of the A. marina site was significantly higher, which was closely related to relatively higher diurnal average CO₂ emission rate, soil available nitrogen content and soil net nitrification rate of the A. marina site. Moreover, soil samples of the A. marina site were more responsive to simulated tides and the addition of nitrogen than those of the K. obovata site.     

长江口滨岸潮滩柱样沉积物与孔隙水中氮的垂直分布特征

对长江口滨岸潮滩柱样沉积物及孔隙水中NH4^ -N、NO3^--N和NO2^--N的剖面进行了分析。结果表明,沉积物和孔隙水中NH4^ -N,NO3^--N和NO2^--N剖面分布基本一致,其中NH4^ -N含量最高,这说明有机质的降解反应主要是在缺氧或无氧环境中进行的;沉积物中有机质含量与NH4^ -N含量线性相关;NO3^--N和NO2^--N在剖面中以0～20cm变化剧烈,说明表层和深层有机质的降解程度发生改变。     

1988年以来气候控制的南流江河口红树林扩张

基于卫星图像重建了近30年来广西南流江河口区一片红树林的扩张过程,结果表明：自1988年至2013年,该红树林向海显著扩张,面积由60公顷增加为134公顷。红树林的自然扩张并非渐进式,而是集中发生于某些特定时期。为了研究控制红树林扩张的动力机制,本文研究了近几十年来红树林潮坪高程演变和区域气候变化过程,同时也分析了水动力状况和营养盐供应的变化情况。研究表明：在滩面高程达到红树林幼苗存活最低高程的前提下,台风强度、频率和冬季低温是控制该红树林扩张的关键因素。红树林湿地的显著扩张只发生在台风强度和频率较低、冬季较为温暖的时期。而在台风频率和强度较高、冬季较为寒冷的时期,由于红树林幼苗难以存活,红树林则难以扩张。在过去几十年间,由于该区域适宜红树林扩张的时期较为罕见,从而导致了红树林扩张过程的不连续性。与气候因素相比,营养供应和水动力状况并不是控制该红树林扩张的关键因素。     

长江口潮差中长期变化对河口生态环境的影响

为了探讨长江口潮差的中长期变化对生态环境的影响,利用小波变换法对1972—2018年该河口代表性潮位站的潮差序列(共66336个数据)进行周期性分析。结果表明,该站潮差除了常见的15 d大、小潮周期外,还有变幅约19 cm(相当于多年平均潮差的7.5%)的0.5 a周期和变幅约16 cm(相当于多年平均潮差的6.3%)的18.5 a周期。月均潮差极大值出现在3月和9月,极小值出现在6月和12月。年均潮差极大值出现在1977,1996和2015年,极小值出现在1986年和2005年。上述潮差变化在时间上与长江口灾害性盐水入侵、悬沙浓度长周期变化以及水下三角洲冲淤转变等重大事件存在明显的对应关系。结论认为,上述中长期潮差周期变化对长江口生态环境具有不可忽视的潜在影响,在今后对河口生态环境的研究中应得到重视。     

Variations in the natural abundance of 15N in estuarine suspended particulate matter: A specific indicator of biological processing

In this study, the ¹⁴N:¹⁵N ratio of suspended particulate material collected from the Tamar river estuary, south-west England, is described. Three populations of particles, distinguishable by their ¹⁵N content, were observed. This investigation has shown that populations of estuarine particles are generated by biological transformations in situ and that the ¹⁵N content of estuarine particles does not merely reflect hydrodynamic mixing of the freshwater and seawater source particulate material.     

The exchange of organic carbon in basin mangrove forests in a southwest Florida estuary

The magnitude and seasonality of organic carbon exchange was estimated for two basin mangrove forests in Rookery Bay, Florida. Runoff and tidal inundation in the forests were seasonal with half the annual total of each occurring from August to October. In each forest there were 152 tides yr^?1 with a cumulative depth of about 12 m. Total organic carbon increased in bay waters exporting from the mangroves following a flood tide and peak concentrations were associated with export due to rainfall. The amount of net export from each basin forest was similar, although the concentration of organic carbon in each were different. Monthly net organic carbon export was proportional to the cumulative tidal amplitude within the forest. Total organic carbon export was 64 gC m^?2 yr^?1 and DOC was 75% of the total. A comparison of organic carbon export among riverine, fringe and basin mangroves suggests that tidal hydrology influences the proportion of litter fall that is exported from mangroves; and the magnitude of this organic carbon export from mangroves is related to the cumulative tidal amplitude within the forests.     

夏季长江口水体层化和潮汐作用对颗粒氮、磷运移的影响

于2018年7月对长江口及其邻近海域水体中的海洋化学参数进行了3个连续站和5个大面站的调查,分析了该海区水体层化和潮汐作用对颗粒氮(PN)和颗粒磷(PP)的影响.结果表明,该海区PN浓度为0.75～27.42μmol·L-1,平均值为5.39μmol·L-1;PP浓度为0.07～2.05μmol·L-1,平均值为0.3...     

Analysis of Interannual Variations of Inorganic Nitrogen in the Bohai Sea

According to the Bohai Sea cross-section data during 1985～1998, the high concentration inorganic nitrogen in the Bohai Sea section bottom layer water nearshore diffused and transferred to the middle of the Bohai Sea year after year. The interannual variations of the concentration of inorganic nitrogen in the Bohai Sea section bottom layer water may reflect the degree of eutrophication more steadily. The nitrate nitrogen and nitrite nitrogen are used to show quasi-equilibrium state interannual variations, but with the aggravation of seawater pollution, the quasi-equilibrium state of interannual variations has been broken and the marine biological-chemical processes can only maintain the secondary part of the interannual variations in a quasi-equilibrium state, but are not sufficient to prevent the main pan of interannual variations from deviating from the quasi-equilibrium state. The spatial distributions of inorganic nitrogen would be affected by the reproduction and swarming of marine life.     

Tidal effect on dynamics of pore water nitrate in intertidal sediment of a eutrophic Estuary

To evaluate the effect of the tidal cycle on the pore water nitrate dynamics in intertidal sediment, concentrations of inorganic nitrogen in water and sediment were monitored during tidal cycles in the mud flat of Tama Estuary, Japan. During submergence, nitrate concentration was highest in the overlying water and decreased monotonically with increasing depth in the sediment, suggesting that the primary source of nitrate in the sediment was nitrate transported from the overlying water. Pore water nitrate decreased remarkably during the initial 3–4 hours after the onset of exposure. Thereafter, it was constant or slightly increased until tidal flooding.In situ accumulation of nitrate at the end of exposure, however, did not exceed the nitrate concentrations in the overlying water. The inhibition of nitrate reduction and the stimulation of nitrification would explain the change of nitrate concentration, both consistent with the input of oxygen into the sediment following a 10 mm drop of the water table. In Tama Estuary sediments, the effect of the tidal cycle on the removal of combined nitrogen is rather negative, because high nitrate concentrations in the overlying water canceled the positive effect of nitrate accumulation by nitrification during exposure, while tidal oxygen intrusion have an inhibitory effection sedimentary denitrification.     

钱塘江河口潮波特性变化及原因剖析

为掌握钱塘江河口潮波特性的响应机制,采用小波分析法研究了该河口 6 个潮位长期观测站的年平均高、低潮位及年平均涨潮历时等时间序列的变化特征,结合该河口实施的治江缩窄工程及径流周期性变化,探讨了该河口潮波特性时空变 化的因果关系。结果表明：1953—2017 年,钱塘江河口呈现出高潮位显著抬升、涨潮历时缩短,低潮位在河口上段略有抬高、中段大幅抬升、下段变化不大的趋势;受治江缩窄工程进展、位置以及径流周期性变化等影响,各站潮波特性的变化在时间上存在差异;钱塘江河口的治江缩窄工程加剧了河口下段的潮波变形和潮波反射,增强了河口上、中段的河流特性,导致高潮位抬升、涨潮历时缩短,是造成潮波特性变化的主要原因;径流直接影响河口上、中段的潮位和潮流,此外,还通过流速变化改变河床地形而间接影响潮波特性。     

珠江口夏季水体中的氮和磷

根据1999年7月17～28日于珠江口现场调查和实验的资料,研究夏季水体中氮、磷的分布、形态变化和初级生产力的限制因素.结果表明该海域氮含量高,N/P属于世界上高值区之一.从河口向外海运输过程中,氮和磷的形态和浓度均有剧烈的变化.虽然氮在中途中有新源的补充;但由于外海水的入侵稀释、生物吸收和形态变化的迁移作用,NO₃-和可溶无机氮的浓度总的变化趋势仍是随盐度增大而大幅度地降低,以至珠江口外出现N/P低于16.由于夏季水体层化稳定,在表、底层其生物地球化学变化方向相反,PO₄3的浓度变化互成镜像关系并可按盐度分为3段不同特征的反应区.初级生产力的限制因素在大部分区域是磷,但从口门至最大浑浊带和口外区则分别是浊度(或光照)及可溶无机氮.现场培养实验再现了真光层和底层氮和磷的生物地球化学过程差异并表明磷的循环和再生比氮迅速;在可溶无机氮浓度大且高N/P的海域,磷的再生可成为水华的引发因素,而氮被耗尽却是水华消亡的原因.总体上夏季该区水体氮的迁出率比磷高.于水体层化稳定的区域,氮和磷的生物地球化学作用在真光层以浮游生物吸收占优势、在下层以有机物的降解和可溶无机态的再生为主,当层化消失、上下水体充分混合则可完成循环.     

黄河入海口湿地区底质重金属污染的Pb同位素示踪

利用等离子体质谱仪(ICP-MS)和多接收同位素质谱仪(HR-MC-ICP-MS)等技术,对黄河入海口湿地区3个典型区(湿地保护区、采油区和河道)表层沉积物进行了系统的重金属微量元素和Pb同位素分析。结果表明,湿地保护区、采油区和黄河河道三个子区域表层沉积物重金属含量依次降低,受粒度控制明显,且符合第一类沉积物质量标准,处于较清洁水平。Pb同位素数据表明,黄河入海口湿地保护区表层沉积物样品207 Pb/206 Pb和208 Pb/206 Pb比值(0.839,2.090)与已发表文献的中国黄土207Pb/206Pb和208 Pb/206 Pb比值(0.841,2.083)接近,表明黄河湿地保护区内表层沉积物中的重金属Pb的主要来源为黄河自然源(黄土)。采油区及河道样品207 Pb/206 Pb,208 Pb/206 Pb比值(0.848,2.100;0.849,2.105)均高于湿地保护区样品,介于黄河悬浮体(0.865,2.131)及中国黄土之间,表明采油区和河道表层沉积中的Pb主要来源于自然源和人类生产活动。     

Decomposition rate and invertebrate colonization of seagrass detritus along a hydrodynamic gradient in a Mediterranean coastal basin: The Stagnone di Marsala (Italy) case study

Seagrass leaf litter decomposition is a key component of marine carbon flow driven by both biotic and abiotic factors, including water movement. In this study, we analyse Posidonia oceanica litter decomposition and invertebrate colonization in three sites with different hydrodynamics in a coastal basin. Litterbags were put on the sea bed along a gradient of distance from the open sea, implying a different level of water exchange. Leaf litter mass loss and carbon and nitrogen concentration were analysed, and density and biomass of benthic invertebrates colonizing litterbags were recorded after 3, 7, 14, 47, 101, 152 and 221 days. Results showed that in the most sheltered site, the leaf litter decomposition rate, the invertebrate density and biomass and the detrital carbon release were the lowest. The reduction of the decomposition rates of seagrass leaves in the site characterized by low hydrodynamic forces may promote organic matter burial and carbon stocks, emphasizing the role of coastal basins such as ponds and lagoons as sinks of carbon and the important role of seagrass detritus in the Blue Carbon global balance.     

Studies of a mangrove basin,Tuff Crater,New Zealand: I. Mangrove biomass and production of detritus

The mangrove, Avicennia marina var. resinifera in a tidally-flooded explosion crater, Tuff Crater, near the southern latitudinal limit of mangroves in New Zealand adopts two distinct growth forms, taller tree-like mangroves up to 4 m tall along the banks of the tidal creek, and low stunted shrub mangroves less than 1 m tall on the mudflats. Twelve trees were felled and on the basis of a biomass/height relationship for the taller trees and a biomass/canopy width relationship for the lower, above-ground biomass (excluding pneumatophores) was estimated. Average above-ground biomass for the taller mangrove was estimated to be 104·1 t ha^?1 and for the lower 6·8 t ha^?1. While the value for the taller mangroves is similar to figures reported for more complex tropical mangroves, the fact that 94% of the basin is covered by low generally sparse mangroves means that total biomass for the basin is estimated to be 153 t, an average of only 7·6 t ha^?1. Litter-fall beneath the taller mangroves is estimated as 7·6±2·5 t ha^?1 a^?1 and beneath the lower mangroves 3·3±0·5 t ha^?1 a^?1. The value for the taller mangroves is similar to that reported from mangroves in many other parts of the world, but because of the extensive low sparse mangroves the total for the basin is estimated as 53·7 t a^?1, an average rate of 2·7 t ha^?1 a^?1, a very low rate of litter-fall when compared with elsewhere. Decomposition of mangrove leaves occurs relatively rapidly with leaves losing half their dry weight in 10 weeks and then continuing to degrade but at a slower rate. Substrate sediment samples contain high organic matter content, and although some organic matter appears to be exported via the tidal creek, a proportion of the detrital production is evidently recycled in situ.     

福建闽江口和九龙江口外线状沉积沙体特征

福建沿海强潮河口闽江口和九龙江口外均发育有一定规模的线状沉积沙体,通过多波束调查采集数据和浅剖、沉积物资料的分析,对此类沙体特征进行研究,初步认为其为潮流沙脊。结果表明:在平面分布上,闽江口外潮流沙脊走向近SW-NE向,沙脊局部连片;九龙江口外沙脊走向近ENEWSW向,沙脊末端有分叉现象。分析现代海洋环境作用并结合沙脊规模、水深和河口相对关系的研究显示,沙脊主体规模基本稳定,现代水动力仅对沙脊表面有改造作用。在潮流、波浪和近岸余流的共同作用下沙脊脊顶部略显平滑,两翼坡度较缓,其沉积物组成以粒度较粗的古河口砂质浅滩砂为主,沉积主体为全新世海平面上升时期,近岸河口环境的古水下三角洲遭受潮流侵蚀而成。     

稳定碳、氮同位素在生态系统研究中的应用

在简要介绍了稳定同位素测定方法之后 ,对稳定碳、氮同位素在生态系统领域中关于系统的碳源、能量流动、营养结构、污染物的生物放大作用及系统稳定性变化的应用研究作了较为系统的论述 ,并对稳定碳、氮同位素在赤潮研究、环境污染治理、生态动力学建模及有机分子化合物系列示踪技术等方面的应用提出展望